Roller pump

ABSTRACT

To prevent damage to a tube in a roller pump which pumps a fluid contained in the tube by squeezing it against an inner wall surface of a housing with a roller, so that the tube can be used continuously for a long time. A depression which a part of the tube enters when squeezed with the roller is formed on at least one of a roller surface of the roller and the inner wall surface of the housing. This alleviates a load on the tube, thereby preventing damage to the tube. Alternatively, the roller may include a plurality of disc rollers that are separately rotatable. This reduces differences in frictional force acting upon the tube when squeezed by the roller, thereby preventing damage to the tube. According to these constructions, the tube can be used continuously for a long time.

TECHNICAL FIELD

The present invention relates to a roller pump that pumps a fluid contained in a tube in a blood circuit, an infusion circuit, and the like.

BACKGROUND ART

In recent years, roller pumps which pump fluids inside medical tubing are widely used in medical facilities.

For instance, treatment is carried out using an extracorporeal blood system that takes a patient's blood outside the body for processing such as purification and oxygenation and then return the blood to the patient. This extracorporeal blood system was first applied to hemodialysis, and is nowadays used for pump-oxygenators, artificial livers, and plasma separators too.

In the extracorporeal blood system, a blood circuit is formed using tubes and connectors. Conventionally, polyvinyl chloride tubes are widely used, but recently olefin tubes are used too. Roller pumps are employed to propel blood carried in such tubing. In dialysis, roller pumps are also used to propel dialysate to a dialyzer through tubing.

A typical roller pump includes a housing with a curved inner wall surface to which a tube is to be attached, a rotor connected with a rotor of a motor and axially supported in the housing, and rollers rotatably fixed to the rotor. As the rotor rotates, the rollers move to squeeze the tube against the inner wall surface of the housing, thereby forcing a fluid in the tube to flow.

Since such a roller pump presses the tube to pump the fluid, a load is exerted on the tube. This being so, when used continuously, the tube is worn away or scraped away. The tube may even be cracked depending on its material. This makes it difficult to use the tube continuously for a long time. Especially when the tube is formed from an olefin such as PP (polypropylene), the tube tends to be worn or scraped away or cracked.

Also, if an inner wall of the tube is scraped away, the removed tube material gets mixed in with the fluid, thereby damaging the fluid.

DISCLOSURE OF THE INVENTION

The present invention aims to prevent damage to a tube in a roller pump which pumps a fluid contained in the tube by squeezing it against a housing with a roller, so that the tube can be used continuously for a long time.

The stated aim can be achieved by a roller pump that pumps a fluid contained in a tube by squeezing the tube against a wall surface of a housing with a roller, characterized in that a depression which a part of the tube enters when squeezed with the roller is formed on at least one of a roller surface of the roller and the wall surface of the housing.

According to this construction, a part of the tube enters the depression when squeezed with the roller. This alleviates a load on the tube, so that damage to the tube is prevented. As a result, the tube can be used continuously for a long time without a tube material getting mixed in with the fluid.

Here, the depression may be continuously formed around a circumference of the roller surface of the roller.

Here, the depression may be formed as a ring (i.e. concentric with the roller surface).

Here, the depression may be formed in the middle of the roller surface in a direction of a rotation axis of the roller.

Here, a projection may be formed on the wall surface of the housing in an area corresponding to the depression on the roller surface of the roller.

Such a projection aids the part of the tube to enter the depression.

Here, the projection may be continuously formed a long the tube.

Here, a width of the depression in a direction of a rotation axis of the roller may be no smaller than a wall thickness of the tube and no larger than three times the wall thickness of the tube.

Here, a depth of the depression may be no smaller than a wall thickness of the tube.

The stated aim can also be achieved by a roller pump that pumps a fluid contained in a tube by squeezing the tube against a wall surface of a housing with a roller, characterized in that the roller includes a plurality of disc rollers which are separately rotatable.

According to this construction, differences in frictional force acting upon the tube when squeezed with the roller are reduced. This prevents damage to the tube. As a result, the tube can be used continuously for a long time without a tube material getting mixed in with the fluid.

Here, at least three disc rollers of the plurality of disc rollers may contact the tube when the tube is squeezed with the roller.

According to this construction, the differences in frictional force on the tube are more effectively reduced.

Here, a gap which a part of the tube enters when squeezed with the roller may be provided between adjacent disc rollers of the plurality of disc rollers.

According to this construction, a part of the tube enters the gap when squeezed with the roller. This alleviates a load on the tube, with it being possible to prevent damage to the tube.

Here, a width of the gap may be no smaller than a wall thickness of the tube and no larger than three times the wall thickness of the tube.

Here, the wall surface of the housing may be a curved inner wall surface of the housing, wherein a rotor which moves the roller along the inner wall surface of the housing is provided in the housing, with the roller being rotatably attached to the rotor.

The above effects can be achieved with such a typical roller pump. The above effects can equally be achieved with any roller pump that pumps a fluid contained in a tube by squeezing it against a housing with a roller.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a front view of a roller pump to which embodiments of the invention relate.

FIG. 2 is a perspective view of a roller in the first embodiment of the invention.

FIG. 3 is a representation of how a tube is deformed when pressed by the roller shown in FIG. 2 and when pressed by a conventional roller.

FIG. 4 is a representation of how a tube is deformed in a roller pump which is a modification to the first embodiment.

FIG. 5 is a representation of how a tube is deformed in a roller pump which is another modification to the first embodiment.

FIG. 6 is a perspective view of a roller in the second embodiment of the invention.

FIG. 7 is a representation of how a tube is deformed when pressed by the roller shown in FIG. 6.

FIG. 8 shows a situation where a tube is squeezed with a conventional roller.

BEST MODE FOR CARRYING OUT THE INVENTION

A roller pump of the present invention is descried byway of embodiments below, with reference to the drawings.

Overall Construction of a Roller Pump

FIG. 1 is a front view of a roller pump 1 to which embodiments of the invention relate.

In the drawing, the roller pump 1 is roughly made up of a case 100 and a pumphead unit (central unit) 200.

The case 100 contains various control units (not illustrated). The case 100 is also equipped with a display unit 130 and an operation unit 120 on its outer face.

The pumphead unit 200 is secured to the bottom of the case 100. The pumphead unit 200 includes a housing 10 having a curved inner wall surface 11 to which a tube 50 is to be attached, a rotor 20 axially supported in the housing 10, and a plurality of rollers 30 mounted on the rotor 20.

The tube 50 carries a fluid, and is made of an elastic material. Example materials of the tube 50 include polyvinyl chloride, and an olefin elastomer such as polybutadiene. The tube 50 is laid along the inner wall surface 11 of the housing 10 in the form of a circular arc.

The rotor 20 has a plurality of roller mounting units 21 (eight in FIG. 1) which are spaced with each other on its periphery. The rotor 20 is connected with a rotor of a motor (not illustrated). A driving power of the motor (i.e. a rotational power of the rotor of the motor) is transmitted to rotate the rotor 20.

The rotor 20 is positioned to create a gap 40 in which the tube 50 can be inserted, between its periphery and the inner wall surface 11 of the housing 10.

The rollers 30 are each shaped like a cylinder, and are made of aluminum or a resin as one example. The rollers 30 are axially supported by the roller mounting units 21 so as to be rotatable about a rotation axis 35 (see FIG. 2).

The rollers 30 are positioned to project from the periphery of the rotor 20. This being so, a gap 41 between the rollers 30 and the inner wall surface 11 of the housing 10 is smaller than the gap 40 and therefore smaller than an outside diameter of the tube 50.

According to this construction, the rollers 30 move as the rotor 20 rotates, as shown in FIG. 1. During this, the rollers 30 rotate while contacting the tube 50 and pressing it against the inner wall surface 11. This squeezes the tube 50 and pumps the fluid contained in the tube 50.

Here, since the rollers 30 are rotatably attached to the roller mounting units 21, the rollers 30 turn free on their own when coming into contact with the tube 50. Accordingly, a pressure exerted on the tube 50 by the rollers 30 is smaller than in the case where the tube 50 is pressed by rollers which do not turn free.

Characteristics and effects of the rollers 30 are explained in detail below, based on the first and second embodiments of the invention.

First Embodiment

FIG. 2 is a perspective view of a roller 30 in the first embodiment.

In the drawing, the roller 30 is constricted in the middle in a direction of the rotation axis 35, to create a depression 31. The depression 31 is a ring-shaped groove formed around a whole circumference of a roller surface 30A of the roller 30.

Which is to say, the roller surface 30A is symmetrical with respect to the rotation axis 35, and is smaller in diameter in the middle in the direction of the rotation axis 35 than in the other parts.

(Effect of the Roller 30 in the First Embodiment)

FIG. 3A shows a situation where the tube 50 is pressed by the roller 30 having the depression 31, whereas FIG. 3B shows a situation where the tube 50 is pressed by a conventional roller 60 having no depression.

In FIG. 3B, when the roller 60 presses the tube 50 which is laid on an inner wall surface 111 of a housing 110, a middle part 50 a of the tube 50 in a direction of a rotation axis 65 of the roller 60 is acted upon by a force of stretching to both side parts 50 b, as indicated by hollow arrows. As a result, a heavy load is exerted on the tube 50 (especially in the side parts 50 b). This is one of the major causes of damage to the tube 50.

In FIG. 3A, on the other hand, when the roller 30 presses the tube 50 which is laid on the inner wall surface 11 of the housing 10, the side parts 50 b are pressed flat by the roller surface 30A, but the middle part 50 a partially enters the depression 31. In other words, when the tube 50 is pressed by the roller 30, the middle part 50 a can partially escape into the depression 31. This alleviates the load on the tube 50 (especially in the side parts 50 b) Hence damage to the tube 50 is prevented.

Since the roller 30 can be formed simply by forming the depression 31 in a conventional roller, a manufacturing process is easy. Also, the manufacturing process is easier when compared with the case of forming a depression in a housing.

(Details of the Depression 31)

If a width w of the depression 31 (i.e. a width of an open end of the depression 31) is smaller than a wall thickness t of the tube 50, part of the tube 50 may not be able to enter the depression 31. Therefore, it is preferable for the width w of the depression 31 to be no smaller than the wall thickness t of the tube 50, to achieve the above effect. Meanwhile, in a state where the tube 50 is pressed by a roller, a width of an internal space of the tube 50 is about (π D/2−2t) (where D is the outside diameter of the tube 50 and t is the wall thickness of the tube 50). This being so, the width w of the depression 31 needs to be no larger than (D/2−2t). Also, if the width w of the depression 31 is larger than three times the wall thickness t of the tube 50 (i.e. 3t), the effect of alleviating the load on the tube 50 by allowing part of the tube 50 to escape into the depression 31 may not be achieved. Accordingly, the width w of the depression 31 is preferably no larger than 3t.

Meanwhile, a depth d of the depression 31 is preferably no smaller than the tube thickness t (t≦d), to allow a sufficient amount of tube to escape into the depression 31. The depth d of the depression 31 is more preferably no smaller than twice the tube thickness t (2t≦d).

Regarding the position and number of depressions, a single depression 31 is formed in the middle of the roller 30 in the direction of the rotation axis 35 in FIGS. 2 and 3. Alternatively, two or more depressions may be formed in the roller 30 in the direction of the rotation axis 35. This produces a similar effect, since part of the tube 50 enters each of the depressions as the tube 50 is squeezed with the roller 30. In this case, it is desirable to form the depressions to be as symmetrical as possible with respect to the direction of the rotation axis 35.

Also, to achieve the above effect, it is preferable to continuously form the depression 31 around the circumference of the roller 30 especially in the shape of a ring, as shown in FIG. 2. However, a certain degree of effect can still be achieved even when the depression 31 is formed discontinuously around the circumference of the roller 30.

(Modifications to the First Embodiment)

In the first embodiment, the inner wall surface 11 of the housing 10 is flat in the direction of the rotation axis 35, as shown in FIG. 3A. Alternatively, a projection 11 a may be formed on the inner wall surface 11 in an area corresponding to the depression 31, as shown in FIG. 4.

By doing so, when the tube 50 is squeezed with the roller 30, the projection 11 a aids the middle part 50 a to enter the depression 31. In other words, part of the tube 50 is more smoothly pushed into the depression 31. Hence the load on the tube 50 can be alleviated effectively.

Here, it is preferable to form the projection 11 a continuously along the tube 50.

In the first embodiment, the depression 31 is formed on the roller surface 30A of the roller 30. As an alternative, a depression 12 may be formed on the inner wall surface 11 of the housing 10, as shown in FIG. 5.

In this case, when the tube 50 is squeezed with the conventional roller 60 which has no depression, the middle part 50 a partially enters the depression 12. This alleviates the load on the tube 50 (especially in the side parts 50 b). Hence damage to the tube 50 can be prevented as in the case where the tube 50 is squeezed with the roller 30 having the depression 31.

It should be obvious that the roller 30 having the depression 31 can be combined with the housing 10 with the inner wall surface 11 having the depression 12.

Second Embodiment

FIG. 6 is a perspective view of a roller 30 in the second embodiment.

In the drawing, the roller 30 is formed by a plurality of disc-shaped rollers (hereafter “disc rollers”) 32 which are axially supported by a rotation axis 35 so as to be separately rotatable. Each of the disc rollers 32 moves as the rotor 20 rotates, and separately rotates in contact with the tube 50. FIG. 7 shows a situation where the tube 50 is pressed by this roller 30.

In FIGS. 6 and 7, the roller 30 has three disc rollers 32, namely, one middle disc roller 32 a and two side disc rollers 32 b. However, the number of disc rollers is not limited to such, as the roller 30 may have two disc rollers or four or more disc rollers. Note here that the disc rollers 32 are arranged at predetermined intervals to ease independent rotations.

Thus, the roller 30 has the plurality of disc rollers 32 that are separately rotatable. According to this construction, differences in frictional force acting upon the tube 50 squeezed with the roller 30 are reduced when compared with the case where a conventional roller is used, as explained below. As a result, damage to the tube 50 is prevented.

(Effect of the Roller 30 in the Second Embodiment)

Causes of damage to the tube 50 when the tube 50 is squeezed with a conventional roller include not only the one described in the first embodiment but also the following.

FIG. 8 shows a situation where the tube 50 is squeezed with the conventional roller 60.

As shown in the drawing, when the roller 60 rolls while pressing the tube 50, the tube 50 distorts in its extending direction near the area in contact with the roller 60.

Here, the middle part 50 a distorts more than the side parts 50 b. Also, a contact length of the tube 50 with the roller 60 in a rotation direction of the roller 60 is greater in the middle part 50 a (L1) than in the side parts 50 b (L2). Furthermore, a shifting speed of the roller-contact area on the surface of the tube 50 is different between the middle part 50 a and the side parts 50 b. This being the case, when the tube 50 is squeezed with the roller 60, the middle part 50 a is partially pushed toward the side parts 50 b.

Thus, the shifting speed of the roller-contact area on the surface of the tube 50 is different between the middle part 50 a and the side parts 50 b. On the other hand, a peripheral speed of the roller 60 is uniform for all of the middle part 50 a and the side parts 50 b. This causes different frictional forces to act between the surface of the tube 50 and the surface of the roller 60, thereby damaging the tube 50.

If such differences in frictional force on each part of the tube 50 accumulate, the tube 50 may be twisted or cracked.

When the roller 30 shown in FIG. 6 rolls while pressing the tube 50, the tube 50 distorts in its extending direction near the area in contact with the roller 30 and the middle part 50 a is partially pushed toward the side parts 50 b, in the same manner as in FIG. 8. In this case, however, the disc roller 32 a in contact with the middle part 50 a and the disc rollers 32 b in contact with the side parts 50 b rotate independently from each other. Therefore, a peripheral speed of each of the disc rollers 32 can be varied according to the shifting speed of the corresponding part of the tube 50. This reduces the differences in frictional force acting on the tube 50. Also, by varying the number of revolutions of the disc rollers 32 b with reference to that of the disc roller 32 a, part of the tube 50 can be smoothly pushed from the middle part 50 a toward the side parts 50 b and from the side parts 50 b toward further outside.

By reducing the differences in frictional force acting upon the tube 50 in this way, damage to the tube 50 can be prevented.

(Width, Number, and Interval of the Disc Rollers 32)

Even when the roller 30 has only two disc rollers, the effect of reducing the differences in frictional force on the tube 50 can be produced to some extent. However, if the roller 30 has three or more disc rollers as shown in FIGS. 6 and 7, the middle part 50 a and the side parts 50 b can each be pressed by a separate disc roller. Therefore, the number of disc rollers in the roller 30 is preferably three or more.

Also, any of the disc roller 32 a and the disc rollers 32 b shown in FIGS. 6 and 7 may further be divided by two, thereby providing many thin disc rollers. This enhances the effect of reducing the differences in frictional force on the tube 50.

Furthermore, provision of many disc rollers makes it possible to deal with the case when the tube 50 shifts away from the roller 30, as explained below.

In the example of FIGS. 6 and 7 where the number of disc rollers 32 is three, if the tube 50 shifts away from the roller 30 in the direction of the rotation axis 35, one of the disc rollers 32 b may deviate from the tube 50. However, if the number of disc rollers 32 is four or more, even when the tube 50 somewhat shifts away from the roller 30 in the direction of the rotation axis 35, the middle part 50 a and the side parts 50 b are each pressed by a different disc roller without fail. Hence damage to the tube 50 can be effectively prevented.

In a state where the tube 50 is pressed by a roller, a width of an internal space of the tube 50 is about (π D/2−2t) (where D denotes the outside diameter of the tube 50 and t denotes the wall thickness of the tube 50). This being so, to press the side parts 50 b with the disc rollers 32 b, an interval between the disc rollers 32 b is preferably no larger than (π D/2−2t). In this case, a width Wa of the disc roller 32 a is smaller than (π D/2−2t).

No gap may be provided between adjacent disc rollers 32 (i.e. between the disc roller 32 a and each of the disc rollers 32 b in FIGS. 6 and 7). However, if a gap is provided, such a gap serves to accommodate part of the tube 50 like the depression 31 in the first embodiment. In this case, a gap w1 between adjacent disc rollers 32 is preferably no smaller than the wall thickness t of the tube 50 and no larger than three times the wall thickness t (i.e. 3t), as in the first embodiment.

Modifications to the Embodiments

The roller pump 1 shown in FIG. 1 is provided with the case 100 which includes the display unit 130 and the operation unit 120 and the pumphead unit 200 which is attached to the case 100, but the invention is not limited to such. For example, the display unit and the operation unit may be omitted, or the pumphead unit may be provided separately from the case instead of being attached to the case.

In the roller pump 1 shown in FIG. 1, the tube 50 is set in the housing 10 in a horizontal direction so that the fluid flows from right to left in the drawing, but this is not a limit for the invention, which is equally applicable to any roller pump that pumps a fluid contained in a tube by squeezing the tube against a housing with a roller. For example, the same effect as above can be achieved when the roller 30 of any of the first and second embodiments is applied to a roller pump in which a tube is set to make a U-turn in a housing.

Like the roller pump 1 shown in FIG. 1, a typical construction of a roller pump is such that a rotor to which rollers are rotatably fixed is placed in a housing so as to move the rollers along an inner wall surface of the housing to which a tube is to be attached. The same effect as above can be achieved when the roller 30 of any of the first and second embodiments is applied to such a typical roller pump. The effect can equally be achieved when the roller 30 is applied to any roller pump that pumps a fluid contained in a tube by squeezing it against a housing with a roller.

Example Applications

A roller pump according to any of the above embodiments and modifications can be used in a blood circuit such as a hemodialysis circuit, a pump-oxygenator, an artificial liver, or a plasma separator.

In a hemodialysis circuit, a dialyzer containing a dialyzing membrane (hollow fiber) is connected with a tube for circulating blood and a tube for circulating dialysate. Here, to propel the blood or the dialysate in each tube, the tube is set in the roller pump.

The roller pump may equally be used in an infusion circuit such as a peritoneal dialysis circuit. In an infusion circuit, a tube for circulating an infusion is set in the roller pump.

By employing the roller pump in a blood circuit or an infusion circuit in this way, the tubing that forms the circuit can be used continuously for a long time without a tube material getting mixed in with blood or an infusion.

INDUSTRIAL APPLICABILITY

The invention can be used for a circuit such as a blood circuit or an infusion circuit to prevent damage to tubing that forms the circuit. As a result, the tubing can be used continuously for a long time without a tube material getting mixed in with fluids in the tubing. 

1. A roller pump that pumps a fluid contained in a tube by squeezing the tube against a wall surface of a housing with a roller, characterized in that a depression which a part of the tube enters when squeezed with the roller is formed on at least one of a roller surface of the roller and the wall surface of the housing.
 2. The roller pump of claim 1, wherein the depression is continuously formed around a circumference of the roller surface of the roller.
 3. The roller pump of claim 2, wherein the depression is formed as a ring.
 4. The roller pump of claim 2, wherein the depression is formed in the middle of the roller surface in a direction of a rotation axis of the roller.
 5. The roller pump of claim 2, wherein a projection is formed on the wall surface of the housing in an area corresponding to the depression on the roller surface of the roller.
 6. The roller pump of claim 5, wherein the projection is continuously formed along the tube.
 7. The roller pump of claim 1, wherein a width of the depression in a direction of a rotation axis of the roller is no smaller than a wall thickness of the tube and no larger than three times the wall thickness of the tube.
 8. The roller pump of claim 1, wherein a depth of the depression is no smaller than a wall thickness of the tube.
 9. The roller pump of claim 1, wherein the wall surface of the housing is a curved inner wall surface of the housing, and a rotor which moves the roller along the inner wall surface of the housing is provided in the housing, with the roller being rotatably attached to the rotor.
 10. A roller pump that pumps a fluid contained in a tube by squeezing the tube against a wall surface of a housing with a roller, characterized in that the roller includes a plurality of disc rollers which are separately rotatable.
 11. The roller pump of claim 10, wherein at least three disc rollers of the plurality of disc rollers contact the tube when the tube is squeezed with the roller.
 12. The roller pump of claim 10, wherein a gap which a part of the tube enters when squeezed with the roller is provided between adjacent disc rollers of the plurality of disc rollers.
 13. The roller pump of claim 12, wherein a width of the gap is no smaller than a wall thickness of the tube and no larger than three times the wall thickness of the tube.
 14. The roller pump of claim 10, wherein the wall surface of the housing is a curved inner wall surface of the housing, and a rotor which moves the roller along the inner wall surface of the housing is provided in the housing, with the roller being rotatably attached to the rotor.
 15. A blood circuit in which a blood circulation tube is set in the roller pump of claim
 1. 16. An infusion circuit in which an infusion circulation tube is set in the roller pump of claim
 1. 17. A dialysis circuit comprising: a dialyzer which performs dialysis by having blood and dialysate pass through a dialyzing membrane; at least one of a blood circulation tube and an infusion circulation tube; and the roller pump of claim 1 in which the tube is set and which pumps a fluid contained in the tube to the dialyzer.
 18. A blood circuit in which a blood circulation tube is set in the roller pump of claim
 10. 19. An infusion circuit in which an infusion circulation tube is set in the roller pump of claim
 10. 20. A dialysis circuit comprising: a dialyzer which performs dialysis by having blood and dialysate pass through a dialyzing membrane; at least one of a blood circulation tube and an infusion circulation tube; and the roller pump of claim 10 in which the tube is set and which pumps a fluid contained in the tube to the dialyzer. 